LONGMONT, Colo. (CBS4) – A part-time school janitor is now behind bars after police say he had a sexual relationship with a 13-year-old girl.

Boulder County sheriff’s deputies said they found the girl and Travis Bowden, 24, together in a car at Lagerman Reservoir Saturday morning.

Bowden went before a judge on Monday. He’s charged with one count of sexual assault on a child. More charges could still be filed.

“The deputies quickly picked up upon, ‘This is not right; a 24-year-old man and a 13-year-old girl.’ When they questioned her she admitted to having a sexual relationship,” Jeff Satur with Longmont police said.

Satur said Bowden had been molesting the girl for several months in a Longmont neighborhood where the two live.

Bowden was a fill-in custodian for the St. Vrain Valley School District and before that at a local church. Police suspect there could be more victims. The school will notify parents Tuesday with letters to all of its students.

Neighbors told CBS4 Bowden would hang out with children all the time, with some being as young as 7.

“We observed him playing with younger kids. He’s an older adult and so we always wondered,” neighbor Joel Estrada said.

“He made his garage into like a room where he put up a big-screen TV and couches; all the kids hung out,” neighbor Kathy Summers said.

Summers said Bowden is married but has no friends his own age. He has no children.

(credit: CBS)

“Any time your kids are hanging out with older individuals you should be asking, ‘Why?’ ” Satur said.

Neighbors said the victim is being raised by her disabled grandmother and grandfather who they say trusted Bowden.

Bowden remains in jail on a $25,000 bond.

Police haven’t released Bowden’s mug shot because they might need it in a photo lineup for other possible victims.